Last week, there was some discussion on lack of volume with the x-50 and I commented that I was having the same problem. I didn't bother to check to see if another brand of phones would work or not until I read John LA's post. I have used Killer B's exclusively and they would work with the Xterra, but I just couldn't get the volume higher no matter if I adjusted the detector or the headphones. Today, I got out my Koss 30's that came with my Explorer and plugged them in and took the detector outside. The volume was way too loud. These phones are fixed volume and I had to turn the detector volume down to 12 to get to a level that didn't hurt my ears. I don't know squat about ohms and impedence, but it is my guess that this is where my problem was. Personally, I don't like the tones of the Koss phones compared to the Killer Bs, but there is defintely plenty of volume with the Koss 30's. I thank John La for the advice. HH R.L.